Comment on "Global Positioning System Test of the Local Position Invariance of Planck's Constant"

TL;DR

This paper critiques a previous claim that GPS satellite clock data can test the invariance of Planck's constant, arguing that such limits are not meaningful and clarifying misconceptions about fundamental constant variations.

Contribution

It clarifies the limitations of using GPS clock data to constrain variations in fundamental constants and corrects misconceptions in prior interpretations.

Findings

Limits on dimensional constants variation are not meaningful.

Single-clock GPS data cannot constrain fundamental constant variations.

Previous Earth-based LPI experiment interpretations are corrected.

Abstract

In their Letter, Kentosh and Mohageg [Phys. Rev. Lett. 108, 110801 (2012)] seek to use data from clocks aboard global positioning system (GPS) satellites to place limits on local position invariance (LPI) violations of Planck's constant, h. It is the purpose of this comment to show that discussing limits on variation of dimensional constants (such as h) is not meaningful; that even within a correct framework it is not possible to extract limits on variation of fundamental constants from a single type of clock aboard GPS satellites; and to correct an important misconception in the authors' interpretation of previous Earth-based LPI experiments.